Will the world end on 21st December 2012 because of the end of the Mayan calendar or because the winter solstice is "aligned" with the Milky Way?

Update: We, the Ask an Astronomer volunteers, enthusiastically recommend cosmophobia.org. This is a really excellent website that delves into all the details about the 2012 doomsday hoax, and then explains in great detail how none of it lines up with real science.

It appears that Mayan ideas about time keeping and calendars were very cyclical. This is actually easy to understand because it's quite like our calendar which has cycles of various sizes very familiar to us. For example there is a:

1 Jan every year

day 1 every month

Monday every week

1am every day

The Mayan cycles were a bit more complex, such that every day in a 52 year period had a unique name from a combination of various different cycles (similar to the idea that there is a Monday 1st January only every 7 years or so). This 52 year cycle has is called a Calendar Round. To keep track of dates on longer time scales the Mayans then had what's known as the Long Count, which provides a unique numerical indicator for each day. Mayans did not count in base ten like we did, but usually instead in base 20 (although not always). The Mayan long count can be summarized as:

#days

Mayan count

1

1 kin

20

20 kin

1 uinal

360

360 kin

18 uinal

1 tun

7200

7200 kin

360 uinal

20 tun

1 kactun

144000

144000 kin

7200 uinal

400 tun

20 kactun

1 bactun

The name for a Mayan epoch apparently translates as 13 bactuns, which you can see is 13*144000 days or 5125.26 years (roughly). There is actually some minor disagreement over when the current Mayan long cycle started, but it was probably either August 11th or 13th 3114 BC, which means it comes to an end on either Dec 21st or 23rd 2012.

As I mentioned above the Mayan calendar was designed to be cyclical, so the fact that the long count comes to an end in Dec 2012, while having some significance for the Maya as the end of a great cycle (much like we celebrated the millennium (incorrectly as it happens) on Dec 31st 1999), does not mean that the "world will come to an end". It's actually true that there are Mayan names for periods of time longer than 13 bactuns, so that their calendar doesn't even end then, and even if it did there is no evidence to suggest that they (or anyone for that matter) have any special knowledge about the end of the world.

There are however a lot of theories knocking around the Internet which use the end of this calendar cycle to predict the end of the world. They often also mention the fact that Dec 21st is the winter solstice, and that the Sun on the solstice that year is "aligned" with the plane of the galaxy. On the winter solstice, the Sun always has a Declination of -23.5 degrees, and a Right Ascension of 18 hours, but exactly where this is on the sky relative to more distant stars changes very slowly due to the "precession of the equinoxes". We have a posted answer explaining this effect but how it's important in this answer (and how it was first noticed) is by the fact that it moves the position of the equinoxes, and solstices with a period of 26,000 years in a complete circle around the sky westward along the ecliptic. So the position of the winter solstice moves 360 degrees in 26,000 years. That means that it moves 360/26000 = 0.01 degrees a year. Defining an exact boundary for the plane of the Milky Way is tough, but it's at least 10-20 degrees wide across much of the sky, meaning that the solstice can be described as being "in the plane of the Milky Way" for 700-1400 years! To put it another way, the winter solstice that just past (2005) was only 0.1 degrees away from where it will be in 2012, a distance smaller than the size of the Sun itself (which is about 0.5 degrees in diameter). In any case the Sun crosses the plane of the Galaxy twice every year as we orbit around it, with no ill effect on Earth.

To conclude:

The Mayan calendar does not predict the end of the world on Dec 12th 2012.

The exact date of the end of the current Mayan Long Count is still a matter of debate amongst Mayan scholars, although it is likely to be around Dec 21 2012.

The Mayan calendar is cyclical, and there are names for cycles longer than 13 bactuns of the Long Count which are coming to an end in 2012.

Even if the Mayans did believe that the world would come to an end at the end of the Long Count (which I don't believe is true), there is no reason to assume that they have any special knowledge which would allow them to make this prediction correctly. You are free to believe the Sun won't come up tomorrow, but it will anyway....

The fact that the winter solstice on 2012 is "aligned" with the plane of the Galaxy has no significance.

It takes the winter solstice 700-1400 years to cross the plane of the Galaxy.

The solstice last year (2005) was within 0.1 degrees (or 1/5th the size of the Sun) of where it will be on 2012.

The Sun crosses the plane of the Milky Way twice every year with no ill effect.

Dec. 2012 update: Here's another informative page about 2012 and the Mesoamerican Long Count calendar: It's Not the End of the World. Two of the best sites about the Classic Maya and other Mesoamerican cultures are Mesoweb and FAMSI.

Jun. 2015 update: Turns out the world didn't end...science was right after all!

About the Author

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

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